There are many kinds of motor powered devices which are currently used in automobiles, and they are required to be light-weight and compact. Such a motor powered device typically includes a cylindrical metal case serving also as a magnetic yoke for its motor unit, and one end of the case is closed so as to accommodate a bearing for supporting one end of a rotor shaft of the motor unit while the other end of the motor case is provided with a flange for mounting an end plate thereon. The end plate accommodates another bearing for the rotor shaft. It is advantageous to utilize the end plate as a part of the case for a speed reduction gear as such a motor unit is typically equipped with a speed reduction gear unit. The end plate may be made of cast metal, but it is more advantageous in terms of manufacturing cost to make it from molded synthetic resin.
However, particularly when the end plate is made of synthetic resin, some difficult arises in ensuring the precision of the plane onto which the flange of the motor case abuts, and an exact alignment of the central axial lines of the motor unit and the end plate, in particular those of the two bearings supporting the two ends of a rotor shaft, is difficult to achieve because of the deformation of the end plate as it is cooled after being molded. The mutual alignment of the two bearings is important in ensuring the quiet operation of the motor, the durability of the bearings, and the reduction of the friction loss of the motor unit. It is conceivable to appropriately shape the molding die by taking into account the deformation which the molded end plate is expected to undergo after being molded. However, it will require a special machining process which is time consuming and requires a special skill. Alternatively, the mounting surface may be machined after it is molded. However, it also will require an additional machining process which adds to the manufacturing cost. Thus, it has been desired to obtain a motor case end plate structure which is economical to manufacture and can offer a high dimensional accuracy.